KR20170066085A - Hydraulic system and hydraulic control method for construction machine - Google Patents

Abstract

The hydraulic system of the construction machine selectively supplies the hydraulic fluid from the hydraulic pump to the boom head chamber and the boom rod chamber of the boom cylinder via the boom head hydraulic line and the boom rod hydraulic line A main control valve having a boom control spool, a regeneration device connected to the boom head chamber of the boom cylinder through a hydraulic regeneration line and regenerating energy of the boom cylinder, a regeneration device installed in the hydraulic regeneration line, A regeneration valve unit having a discharge control valve for controlling a flow rate of flowing hydraulic oil, and a regeneration valve unit connected to the main control valve and the regeneration valve unit for controlling their operation and discharging the operating oil through the regeneration unit in a boom- The boom is lowered at a first speed and in the boom down high speed mode, And by discharging the operating fluid through said main control valve and a control unit configured to control so as to lower the boom to the second speed greater than the first speed.

Description

Technical Field [0001] The present invention relates to a hydraulic system and a hydraulic control method for a construction machine,

The present invention relates to a hydraulic system and a hydraulic control method of a construction machine. And more particularly, to a hydraulic system and a hydraulic control method of a construction machine for controlling a boom cylinder for raising and lowering a boom of a construction machine.

A construction machine such as an excavator can use a hydraulic cylinder to move the front work device up and down. For example, by using the engine power to rotate the hydraulic pump, the hydraulic fluid discharged from the hydraulic pump flows into the boom cylinder through the main control valve, and the boom can be raised while the stroke of the boom cylinder occurs. On the other hand, when the boom is lowered, the working oil can be discharged from the boom cylinder to the drain tank through the main control valve by the self weight of the front working device. In the boom lowering operation, since the potential energy of the front working apparatus is not utilized effectively, the technology for recovering and reusing the energy by a suitable method has been developed.

An object of the present invention is to provide a hydraulic system of a construction machine having a boom energy recovery device capable of increasing the amount of work per hour of a construction machine.

Another object of the present invention is to provide a hydraulic control method using the hydraulic system of the above construction machine.

The hydraulic system of the construction machine according to the exemplary embodiments of the present invention includes a boom cylinder for operating a boom of a construction machine, hydraulic oil from a hydraulic pump to a boom head hydraulic line and a boom rod hydraulic line A main control valve having a boom control chamber and a boom control spool for selectively supplying the boom head chamber and the boom cylinder chamber of the boom cylinder through a hydraulic regeneration line to the boom head chamber of the boom cylinder, A regeneration valve unit provided in the hydraulic regeneration line and having a discharge control valve for controlling a flow rate of hydraulic fluid flowing through the hydraulic regeneration line and a regeneration valve unit connected to the regeneration valve unit and the main control valve, And in the boom-down low-speed mode, the operating oil is discharged through the regenerating device, And a control unit for lowering the boom at a first speed and discharging operating oil through the regenerator and the main control valve in a boom down high speed mode to lower the boom at a second speed higher than the first speed .

In exemplary embodiments, the control unit may include a control valve that applies a pilot signal pressure to open and close the emission control valve.

In exemplary embodiments, the control valve may be an electronically proportional pressure reducing valve.

In the exemplary embodiments, the regeneration valve unit may further include a check valve installed in the hydraulic regeneration line in front of the emission control valve.

In the exemplary embodiments, the regeneration valve unit is provided in a connection line connecting the hydraulic regeneration line and the boom rod chamber, and a part of the hydraulic fluid discharged through the hydraulic regeneration line is connected to the boom rod chamber of the boom cylinder And may further include an on-off valve for selectively supplying the on-off valve.

In the exemplary embodiments, the hydraulic system of the construction machine may include a control unit for operating the boom and a control valve provided between the control unit and the main control valve, for bypassing control pressure from the control unit to the main control valve And may further include a valve.

In the exemplary embodiments, the control unit may control to open the discharge control valve in the boom-down low-speed mode and to block control pressure from the operating portion from being transmitted to the boom control spool.

In the exemplary embodiments, the control unit may open the discharge control valve in the boom-down high speed mode and control the control pressure from the operating portion to be transmitted to the boom control spool.

In the exemplary embodiments, the working fluid from the boom head chamber may be discharged to the drain tank via the boom head hydraulic line and the boom control spool.

In exemplary embodiments, the playback apparatus includes a hydraulic motor connected to the hydraulic regeneration line, and the hydraulic motor is connected to a drive shaft of the engine and can provide a rotational force to the hydraulic pump.

In exemplary embodiments, the playback apparatus may further include an accumulator connected to the hydraulic regeneration line.

In the exemplary embodiments, the hydraulic system of the construction machine may further include an on-off valve installed on the hydraulic regeneration line connected to the accumulator for selectively supplying the hydraulic fluid to the accumulator.

In another aspect of the present invention, there is provided a method of controlling a hydraulic pressure of a construction machine, the method comprising the steps of: determining whether a boom-down high-speed mode is used in a regeneration mode for recovering boom energy of a construction machine; When the boom-down high speed mode is not selected, operating oil is discharged from the boom head chamber through a regeneration device connected to the boom head chamber of the boom cylinder by the hydraulic regeneration line to lower the boom at the first speed. When the boom-down high-speed mode is selected, the operating fluid is discharged from the boom head chamber through the regenerating apparatus and the operating fluid is discharged from the boom head chamber through the main control valve connected to the boom head chamber of the boom cylinder by the boom- The boom is lowered at a second speed higher than the first speed.

In the exemplary embodiments, determining whether to use the boom-down high speed mode includes selecting either the boom-down low speed mode and the boom-down high speed mode among the playback modes, And when the down low speed mode is selected, blocking the control pressure from the operating portion for operating the boom from being transmitted to the boom control spool of the main control valve.

In the exemplary embodiments, blocking the transmission of the control pressure from the operating portion to the main control valve may include shutting off the bypass valve provided between the operating portion and the main control valve.

In exemplary embodiments, the method may include delivering a control pressure from an operating portion that operates the boom to a boom control spool of the main control valve, when the boom down high speed mode is selected.

In exemplary embodiments, draining hydraulic fluid from the boom head chamber through the regenerator may include opening a discharge control valve installed in the hydraulic regeneration line.

In exemplary embodiments, the playback apparatus may include an accumulator and a hydraulic motor connected to the hydraulic regeneration line.

In exemplary embodiments, the method may further comprise blocking supply of hydraulic fluid to the accumulator in the boom-down high speed mode.

In exemplary embodiments, the method may further include shutting off the hydraulic regeneration line and delivering a control pressure from the operating portion to the boom control spool of the main control valve, when the boom down normal mode is selected .

In a hydraulic system and a hydraulic control method of a construction machine according to exemplary embodiments, boom energy can be recovered through a regenerating device at the time of a boom down, thereby reducing fuel consumption and improving fuel economy. In addition, the boom descent speed can be increased to increase the work amount per unit time, thereby improving the productivity. Particularly, productivity can be maximized in a work in which boom rising and falling operations are repeated (for example, a car work).

However, the effects of the present invention are not limited to the above-mentioned effects, and may be variously expanded without departing from the spirit and scope of the present invention.

1 is a side view of a construction machine according to exemplary embodiments;
2 is a hydraulic circuit diagram illustrating a hydraulic system of a construction machine according to exemplary embodiments.
3 is a hydraulic circuit diagram when the boom-down low-speed mode is selected in the hydraulic system of Fig.
4 is a hydraulic circuit diagram showing a case where the boom-down high-speed mode is selected in the hydraulic system of Fig.
5 is a hydraulic circuit diagram illustrating a hydraulic system of a construction machine according to exemplary embodiments.
Fig. 6 is a hydraulic circuit diagram when the boom-down low-speed mode is selected in the hydraulic system of Fig. 5; Fig.
7 is a hydraulic circuit diagram showing a case where the boom-down high-speed mode is selected in the hydraulic system of Fig. 5; Fig.
8 is a flowchart showing a method of controlling the hydraulic pressure of a construction machine according to exemplary embodiments.

For the embodiments of the invention disclosed herein, specific structural and functional descriptions are set forth for the purpose of describing an embodiment of the invention only, and it is to be understood that the embodiments of the invention may be practiced in various forms, The present invention should not be construed as limited to the embodiments described in Figs.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms may be used for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprise", "having", and the like are intended to specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed as meaning consistent with meaning in the context of the relevant art and are not to be construed as ideal or overly formal in meaning unless expressly defined in the present application .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

1 is a side view of a construction machine according to exemplary embodiments; 2 is a hydraulic circuit diagram illustrating a hydraulic system of a construction machine according to exemplary embodiments. 3 is a hydraulic circuit diagram when the boom-down low-speed mode is selected in the hydraulic system of Fig. 4 is a hydraulic circuit diagram showing a case where the boom-down high-speed mode is selected in the hydraulic system of Fig.

1 to 4, the construction machine 10 includes a lower traveling body 20, an upper swinging body 30 which is swingably mounted on the lower traveling body 20, And may include a cab 50 and a front work unit 60 installed therein.

The lower traveling body 20 supports the upper swing structure 30 and can drive the construction machine 10 such as an excavator using the power generated by the engine 100. [ The lower traveling body 20 may be an endless track type traveling body including an infinite orbit. Alternatively, the lower traveling body 20 may be a wheel-type traveling body including traveling wheels. The upper revolving structure 30 has an upper frame 32 as a base and can rotate on a plane parallel to the ground on the lower traveling body 20 to set the working direction. The cabin 50 is installed on the left front portion of the upper frame 32 and the front working device 60 can be mounted on the front portion of the upper frame 32. [

The front working device 60 may include a boom 70, an arm 80 and a bucket 90. Between the boom 70 and the upper frame 32, a boom cylinder 72 for controlling the movement of the boom 70 may be installed. Between the boom (70) and the arm (80), an arm cylinder (82) for controlling the movement of the arm (80) can be provided. Between the arm 80 and the bucket 90, a bucket cylinder 92 for controlling the movement of the bucket 90 may be installed. As the boom cylinder 72, the arm cylinder 82 and the bucket cylinder 92 elongate or contract, the boom 70, the arm 80 and the bucket 90 can implement various movements and the front working device 60 ) Can perform various tasks. At this time, the boom cylinder 72, the arm cylinder 82, and the bucket cylinder 92 can be extended or retracted by the hydraulic oil supplied from the hydraulic pumps 200 and 202.

On the other hand, an energy recovery system for regenerating the boom energy discharged from the boom cylinder 72 when the boom 70 descends can be provided. The regeneration valve unit 400 having a plurality of valves may constitute a part of the energy recovery system.

As described later, this energy recovery system is configured to accumulate high-pressure hydraulic fluid discharged from the boom cylinder 72 at the time of dropping the boom 70 to the accumulator 500 or rotate the hydraulic motor 510 to assist the output of the engine .

2, the hydraulic system of a construction machine according to exemplary embodiments includes at least one hydraulic pump 200, 202 connected to an engine 100, at least one actuator for operating the front work device A main control valve (MCV) 300 installed in a flow path between the hydraulic pump and the actuator to control the operation of the actuator, a regenerating device for regenerating the energy of the front working device, And a control unit 600 for controlling the operation of the front work unit.

In the exemplary embodiments, the engine 100 may include a diesel engine as a drive source of a construction machine, such as an excavator. At least one hydraulic pump 200, 202 may be connected to the engine 100 via a power take-off (PTO). Although not shown in the drawings, a pilot pump and additional hydraulic pumps may be connected to engine 100. Therefore, the power from the engine 100 can be transmitted to the hydraulic pumps 200 and 202 and the pilot pump.

The hydraulic pumps 200 and 202 may be connected to the main control valve 300 through the hydraulic line 210. The main control valve 300 receives operating fluid from the hydraulic pumps 200 and 202 through the hydraulic line 210 and supplies the hydraulic fluid to the actuator such as the boom cylinder 72, the arm cylinder 82, the bucket cylinder 92, have.

The main control valve 300 can be connected to the plurality of actuators including the boom cylinder 72, the arm cylinder 82 and the bucket cylinder 92 via the high-pressure hydraulic line 220, respectively. Therefore, each of the actuators such as the boom cylinder, the arm cylinder, and the bucket cylinder can be driven by the hydraulic pressure of the hydraulic oil discharged from the hydraulic pumps 200 and 202.

For example, the boom control spool 310 is connected to the boom head chamber 72a and the boom rod chamber 72b of the boom cylinder 72 via the boom head hydraulic line 222 and the boom rod hydraulic line 224, respectively . Accordingly, the boom control spool 310 is switched to selectively supply the hydraulic fluid discharged from the hydraulic pump 200 to the boom head chamber 72a and the boom rod chamber 72b.

The hydraulic oil for driving the actuator may be returned to the drain tank T through the return hydraulic line 212. In the exemplary embodiments, in the boom down normal mode, the operating fluid from the boom head chamber 72a at the time of the boom down is passed through the boom head hydraulic line 222 to the drain tank T via the boom control spool 310, . The operating fluid from the boom rod chamber 72b can be discharged through the boom rod hydraulic line 224 to the drain tank T via the boom control spool 310 when the boom is lifted.

In the exemplary embodiments, the hydraulic system of the construction machine includes a regeneration valve unit 400 installed in the hydraulic regeneration line 230 connected to the boom head chamber 72a to control the supply of hydraulic fluid to the regeneration unit, . ≪ / RTI > The regeneration valve unit may include a variety of valves suitable for an energy recovery system, but not limited to, an emission control valve 410, a check valve 420 and an on / off valve 430.

The hydraulic regeneration line 230 may be connected to the boom head chamber 72a. The hydraulic line from the boom lock valve 76 may be branched from the boom head hydraulic line 222 and the hydraulic regeneration line 230. The discharge control valve 410 is installed in the hydraulic regeneration line 230 and can control the flow rate of the hydraulic fluid flowing through the hydraulic regeneration line 230. The check valve 420 may be installed in the hydraulic regeneration line 230 in front of the discharge control valve 410 to selectively open and close the hydraulic regeneration line 230 in order to hold the boom 70. The open / close valve 240 is provided in a connection line 240 connecting the hydraulic regeneration line 230 and the boom rod chamber 72b to connect a part of the hydraulic fluid discharged through the hydraulic regeneration line 230 to the boom cylinder 72 And can be selectively supplied to the boom rod chamber 72b.

In the exemplary embodiments, the control unit 600 may output the pilot signal pressure to the regeneration valve unit in accordance with the selected control mode to control the supply of hydraulic fluid to the regeneration device via the hydraulic regeneration line 230 have.

The control unit 600 includes a selection unit for selecting a control mode, a control unit for applying an electric signal according to the selected control mode, and first to third control units for outputting a pilot signal pressure corresponding to the applied electric signal Valves.

Specifically, the first control valve may apply the pilot signal pressure corresponding to the electric signal applied from the control unit to the emission control valve 410. The first control valve may be an electronic proportional pressure reducing valve (EPPRV). The pilot signal pressure output from the first control valve is supplied to the left port of the discharge control valve 410 and is switched to the right direction in the drawing of FIG. 2, thereby opening the hydraulic regeneration line 230. The discharge control valve 410 can vary the opening area through which the flow rate is to be passed depending on the position of the control spool. Therefore, the emission control valve 410 can control the opening and closing operation of the hydraulic regeneration line 230 and the flow rate through which the hydraulic regeneration line 230 is passed.

The second control valve may apply the pilot signal pressure corresponding to the electric signal applied from the control unit to the check valve 420. The second control valve may be an electronic proportional pressure reducing valve (EPPRV). The pilot signal pressure output from the second control valve may be supplied to the check valve 420 to open the hydraulic regeneration line 230. The check valve 420 may be a pilot-operated check valve opened by the pilot signal pressure.

The third control valve may apply a pilot signal pressure corresponding to the electric signal applied from the control unit to the on-off valve 430. The third control valve may be an electronic proportional pressure reducing valve (EPPRV). The pilot signal pressure output from the third control valve is supplied to the left port of the on-off valve 430 and is switched to the right side in the drawing of Fig. 2, thereby opening the connection line 240. [ The boom rod chamber 72b is connected to the hydraulic regeneration line 230 through the connecting line 240 so that the deficient flow rate due to the area difference between the head side and the rod side of the boom cylinder 72 Can be supplied to the boom rod chamber (72b) of the boom cylinder (72).

In the exemplary embodiments, the regenerating apparatus can regenerate energy by using high-pressure hydraulic fluid discharged from the boom head chamber 72a of the boom cylinder 72 when the boom 70 descends. The regeneration apparatus may include an accumulator 500 and a hydraulic motor 510. One end of the hydraulic regeneration line 230 may branch and be connected to the accumulator 500 and the hydraulic motor 510, respectively.

The accumulator 500 can store high-pressure hydraulic oil discharged from the boom head chamber 72a of the boom cylinder 72 when the boom is lowered. The hydraulic regeneration line 230 connected to the accumulator 500 is provided with an on-off valve 502 to control the supply / discharge of hydraulic fluid to / from the accumulator 500.

Specifically, the control unit includes a fourth control valve for outputting a pilot signal pressure corresponding to the applied electric signal, and the fourth control valve may apply the pilot signal pressure to the on / off valve 502 . The fourth control valve may be an electronic proportional pressure reducing valve (EPPRV). The pilot signal pressure output from the fourth control valve may switch the on / off valve 502 to shut off supply / discharge of operating oil to / from the accumulator 500.

The hydraulic motor 510 is connected to the drive shaft of the engine 100 and can assist the engine output to provide rotational power to the hydraulic pump. The hydraulic motor 510 may be connected to the drive shaft of the engine 100 via a power transmission unit PTO having a constant gear ratio.

In the exemplary embodiments, the main control valve 300 may include a hydraulic control valve. The boom control spool 310 can be controlled by the pilot pressure proportional to the operation amount of the operating portion 52. [

Specifically, as the operator operates the operating portion 52, the pilot operating oil discharged from the pilot pump and passing through the operating portion 52 can be supplied to the boom control spool 310 through the control flow passages in proportion to the operation amount. Therefore, since the displacement of the boom control spool 310 occurs in proportion to the pilot pressure of the pilot hydraulic oil, the hydraulic fluid from the hydraulic pump 200 can be supplied to the boom cylinder 72 via the boom control spool 310. [

The control unit is provided in the control flow paths between the operating portion 52 and the main control valve 300 to block the control pressure (pilot pressure) from the operating portion 52 from being transmitted to the main control valve 300 A bypass valve 610 may be included. The bypass valve 610 may include an on-off valve.

 In this case, the control unit includes a fifth control valve for outputting a pilot signal pressure corresponding to the applied electric signal, and the fifth control valve applies a pilot signal pressure to the bypass valve 610 . The fifth control valve may be an electronic proportional pressure reducing valve (EPPRV). The pilot signal pressure output from the fifth control valve switches the bypass valve 610 to open or close the control flow paths so that the pilot pressure from the operating part 52 is selectively transmitted to the boom control spool 310 .

The selection unit of the control unit may output a selection signal according to a control mode determined by an operator's selection or control logic to the control unit. The selection unit may select one of the boom down normal mode, the boom down low speed mode, and the boom down high speed mode and output a selection signal corresponding to the selected control mode to the control unit.

For example, the selection unit may determine a control mode through information input through a user interface such as a selection switch. Alternatively, the selection unit may automatically determine the control mode by including control logic that can determine the control mode by calculating the operation pattern information of the operator.

As shown in Fig. 3, when the control mode selected by the operator is a boom-down low-speed mode and the operator inputs a boom-down signal via the operation unit 52, the control unit sets the pilot signal pressure according to the boom- The discharge control valve 410, the check valve 420 and the opening / closing valve 430 to open the hydraulic regeneration line 230. [ Also, the control unit may apply the pilot signal pressure to the bypass valve 610 to block the pilot pressure from the operating unit 52 from being transmitted to the boom control spool 310 of the main control valve 300.

Therefore, in the boom-down low-speed mode, the hydraulic fluid from the boom head chamber 72a of the boom cylinder 72 can be supplied to the regeneration device through the hydraulic regeneration line 230 to recover the position energy of the boom. On the other hand, the pilot pressure from the operating portion 52 is not supplied to the boom control spool 310 of the main control valve 300 by the bypass valve 610, so that the boom control spool 310 is controlled by the boom control spool 310, The hydraulic oil from the boom head chamber 72a does not flow along the boom head hydraulic line 222, Accordingly, the hydraulic fluid discharged from the boom cylinder 72 in the boom-down low-speed mode can be discharged to the drain tank T through the hydraulic motor 510 of the regenerator.

4, when the control mode selected by the operator is the boom-down high-speed mode and the operator inputs the boom-down signal through the operation unit 52, the control unit sets the pilot signal pressure according to the boom- The discharge control valve 410, the check valve 420 and the opening / closing valve 430 to open the hydraulic regeneration line 230. [ The control unit may open the bypass valve 610 to allow the pilot pressure from the operating part 52 to be transmitted to the boom control spool 310 of the main control valve 300. At this time, the control unit may apply the pilot signal pressure to the opening / closing valve 502 of the accumulator 500 to block supply of the operating fluid to the accumulator 500.

The operating fluid from the boom head chamber 72a of the boom cylinder 72 in the boom down high speed mode is supplied to the regeneration apparatus via the hydraulic regeneration line 230 and is supplied to the regeneration apparatus through the boom head hydraulic line 222, To the boom control spool 310 of the boom 300 to recover the position energy of the boom. The operating fluid discharged from the boom cylinder 72 in the boom down high speed mode is discharged to the drain tank T through the hydraulic motor 510 of the regenerating apparatus and discharged to the drain tank T through the main control valve 300 .

When the operating oil is discharged from the boom cylinder 72 due to the self weight of the front working device, the flow passage area through which the operating oil can pass in the boom down high speed mode may be larger than the boom down low speed mode. Accordingly, the boom 70 can be lowered to the first speed V1 in the boom-down low-speed mode and to the second speed V2, which is higher than the first speed V1 in the boom-down high speed mode. Therefore, the workload per unit time of the boom 70 can be increased in the boom-down high-speed mode.

As described above, in the hydraulic system of the construction machine, the boom energy can be recovered through the regenerating apparatus when the boom is lowered, thereby reducing fuel consumption and improving fuel economy. In addition, the boom descent speed can be increased to increase the work amount per unit time, thereby improving the productivity. Particularly, productivity can be maximized in a work in which boom rising and falling operations are repeated (for example, a car work).

On the other hand, when the control mode selected by the operator is the boom down normal mode and the operator inputs the boom down signal through the operation unit 52, the control unit closes the hydraulic regeneration line 230 and transmits the boom down signal via the hydraulic regeneration line 230 It is possible to block the supply to the reproducing apparatus. The control unit may open the bypass valve 610 to allow the pilot pressure from the operating part 52 to be transmitted to the boom control spool 310 of the main control valve 300.

The operating fluid from the boom head chamber 72a of the boom cylinder 72 in the boom down normal mode can be supplied to the boom control spool 310 of the main control valve 300 through the boom head hydraulic line 222 have. In the boom down normal mode, the hydraulic fluid discharged from the boom cylinder 72 may be discharged to the drain tank T through the main control valve 300. On the other hand, the hydraulic regeneration line 230 is closed so that the operating oil from the boom head chamber 72a is not supplied to the regenerating apparatus.

5 is a hydraulic circuit diagram illustrating a hydraulic system of a construction machine according to exemplary embodiments. Fig. 6 is a hydraulic circuit diagram when the boom-down low-speed mode is selected in the hydraulic system of Fig. 5; Fig. 7 is a hydraulic circuit diagram showing a case where the boom-down high-speed mode is selected in the hydraulic system of Fig. 5; Fig. The hydraulic system is substantially the same as or similar to the hydraulic system of the construction machine described with reference to Figures 2 to 4, except that it includes an electrohydraulic control valve. Accordingly, the same constituent elements are denoted by the same reference numerals, and repetitive description of the same constituent elements is omitted.

Referring to Figures 5-7, in the exemplary embodiments, the main control valve 300 may include an electrohydraulic control valve. The boom control spool 310 can be controlled by electron proportional pressure reducing valves 312 that output a secondary pressure (pilot pressure) proportional to an external pressure command signal (control current signal).

Specifically, the control unit receives an electric signal proportional to the operation amount of the operator from the operation unit 52, and outputs the pressure command signal (control current signal) to the electric proportional pressure reducing valves 312 so as to correspond to the electric signal can do. The electronic proportional pressure reducing valves 312 can output a secondary pressure proportional to the pressure command signal to the boom control spool 310, thereby controlling the boom control spool with an electrical signal.

A pair of electromagnetic proportional pressure reducing valves 312 may be provided on both sides of the boom control spool 310, respectively. The electromagnetic proportional pressure reducing valve supplies a secondary pressure proportional to the pressure command signal to the boom control spool, and a displacement of the boom control spool is generated in proportion to the secondary pressure. Accordingly, the operating fluid from the hydraulic pump 200 can be supplied to the boom cylinder 72 via the boom control spool 310.

The control unit may include a control unit for applying a pressure command signal (for example, a control current signal) as an electric signal to the electronic proportional pressure reducing valves 312 of the main control valve 300 according to the selected control mode. The control unit may selectively apply a pressure command signal corresponding to an electric signal input from the operation unit 52 to the electronic proportional pressure reducing valves 312 of the main control valve 300. For example, the control unit does not apply the pressure command signal to the electron proportional pressure reducing valves 312 in accordance with the selected control mode, so that the control pressure (pilot pressure) from the operating unit 52 is applied to the main control valve 300, As shown in FIG.

As shown in Fig. 6, when the control mode selected by the operator is a boom-down low-speed mode operator and the boom-down signal is input via the operating unit 52, the control unit calculates the pilot signal pressure according to the selected control mode The control valve 410, the check valve 420 and the opening / closing valve 430 to open the hydraulic regeneration line 230. [ The control unit does not apply the pressure command signal to the electron proportional pressure reducing valves 312 so that the pilot pressure from the operating part 52 is transmitted to the boom control spool 310 of the main control valve 300 You can block things.

Therefore, in the boom-down low-speed mode, the operating oil from the boom head chamber 72a of the boom cylinder 72 is supplied to the regeneration device via the hydraulic regeneration line 230 to recover the potential energy of the boom, The boom control spool 310 of the boom head chamber 300a does not operate so that the hydraulic fluid from the boom head chamber 72a does not flow along the boom head hydraulic line 222. [ In the boom-down low-speed mode, the hydraulic fluid can be discharged to the drain tank through the hydraulic motor of the recycling apparatus.

7, when the control mode selected by the operator is the boom-down high-speed mode and the operator inputs the boom-down signal through the operation unit 52, the control unit calculates the pilot signal pressure according to the selected control mode as the discharge amount The control valve 410, the check valve 420 and the opening / closing valve 430 to open the hydraulic regeneration line 230. [ The control unit may apply the pressure command signal to the electronic proportioning pressure reducing valves 312 so that the pilot pressure from the operating part 52 is transmitted to the boom control spool 310 of the main control valve 300 have. At this time, the control unit may apply the pilot signal pressure to the on-off valve 502 to block supply of the operating fluid to the accumulator 500.

The operating fluid from the boom head chamber 72a of the boom cylinder 72 in the boom down high speed mode is supplied to the regeneration apparatus via the hydraulic regeneration line 230 and is supplied to the regeneration apparatus through the boom head hydraulic line 222, To the boom control spool 310 of the boom 300 to recover the position energy of the boom. In the boom-down high speed mode, the hydraulic fluid is discharged to the drain tank through the hydraulic motor 510 of the regeneration apparatus and discharged to the drain tank T through the main control valve 300.

When the operating oil is discharged from the boom cylinder 72 due to its own weight of the front working device, it is discharged through the regenerating device in the boom down low speed mode and discharged through the regenerator and the main control valve in the boom down high speed mode. do. Therefore, the flow passage area through which the working oil can pass in the boom-down high-speed mode is larger than that in the boom-down low-speed mode. Thus, the boom 70 can be lowered from the boom down low speed mode to the first speed V1 and from the boom down high speed mode to the second speed V2 which is larger than the first speed V1.

Hereinafter, a hydraulic control method of a construction machine using the hydraulic system of Figs. 2 and 5 will be described.

8 is a flowchart showing a method of controlling the hydraulic pressure of a construction machine according to exemplary embodiments.

2, 5 and 8, one of the boom-down low-speed mode and the boom-down high-speed mode is selected among the regeneration modes for recovering boom energy of the construction machine (S100, S110).

In the exemplary embodiments, the control mode may be determined by operator selection or control logic. The control mode may include a boom down normal mode, a boom down low speed mode, and a boom down high speed mode.

For example, the control mode can be determined through the information inputted by the operator through the user interface such as the selection switch. Alternatively, the control unit can automatically determine the control mode by including control logic that can calculate the operation pattern information of the operator and determine the control mode.

Then, the control pressure from the operation unit 52 is selectively transmitted to the main control valve 300 according to the selected control mode, and the hydraulic regeneration line 230 can be selectively opened and closed.

In the exemplary embodiments, when the boom down low speed mode is selected, when the operator inputs a boom down signal via the operating portion 52, the control pressure from the operating portion 52 is controlled by the boom control of the main control valve 300 The discharge control valve 410, the check valve 420 and the on-off valve 430 are switched to open the hydraulic regeneration line 230 (S300). Subsequently, the hydraulic oil from the boom cylinder 72 is supplied to the regenerator connected to the hydraulic regeneration line 230, and the boom 70 can be lowered (S400)

The operating fluid from the boom head chamber 72a of the boom cylinder 72 in the boom down low speed mode is supplied to the regenerating apparatus through the hydraulic regeneration line 230 to recover the position energy of the boom while the main control valve 300 The boom control spool 310 of the boom head chamber 72a does not operate so that the hydraulic fluid from the boom head chamber 72a does not flow along the boom head hydraulic line 222. [ In the boom-down low-speed mode, the hydraulic fluid can be discharged to the drain tank through the hydraulic motor of the recycling apparatus.

In the exemplary embodiments, when the boom down high speed mode is selected, when a worker inputs a boom down signal via the operation unit 52, the control pressure from the operation unit 52 is controlled by the boom control of the main control valve 300 The discharge control valve 410, the check valve 420 and the open / close valve 430 are switched to open the hydraulic regeneration line 230 (S310). Subsequently, the hydraulic oil from the boom cylinder 72 is supplied to the regenerator connected to the hydraulic regeneration line 230 and the main control valve 300 connected to the boom head hydraulic line 222, so that the boom 70 can be lowered S410).

The operating fluid from the boom head chamber 72a of the boom cylinder 72 in the boom down high speed mode is supplied to the regeneration apparatus through the hydraulic regeneration line 230 and is supplied to the main control valve 300 To the boom control spool 310 of the boom control unit 310 to recover the position energy of the boom. In the boom-down high speed mode, the hydraulic fluid is discharged to the drain tank through the hydraulic motor 510 of the regeneration apparatus and discharged to the drain tank T through the main control valve 300.

When the operating oil is discharged from the boom cylinder 72 by the self weight of the front working device, the flow passage area through which the operating oil can pass in the boom down high speed mode is larger than the boom down low speed mode. Thus, the boom 70 can be lowered from the boom down low speed mode to the first speed V1 and from the boom down high speed mode to the second speed V2 which is larger than the first speed V1.

In the exemplary embodiments, when the boom down normal mode is selected, when a worker inputs a boom down signal via the operation unit 52, the control pressure from the operation unit 52 is controlled by the boom control of the main control valve 300 The discharge control valve 410, the check valve 420 and the open / close valve 430 may be switched to close the hydraulic regeneration line 230 (S320). Subsequently, the hydraulic fluid from the boom cylinder 72 is supplied to the main control valve 300 connected to the boom head hydraulic line 222, and the boom 70 can be lowered (S420).

The operating fluid from the boom head chamber 72a of the boom cylinder 72 in the boom down normal mode can be supplied to the boom control spool 310 of the main control valve 300 through the boom head hydraulic line 222 have. In the boom down normal mode, the hydraulic fluid discharged from the boom cylinder 72 may be discharged to the drain tank T through the main control valve 300. On the other hand, the hydraulic regeneration line 230 is closed so that the operating oil from the boom head chamber 72a is not supplied to the regenerating apparatus.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the following claims. It can be understood that it is possible.

10: Construction machine 20: Lower traveling body
30: upper swivel body 32: upper frame
40: Counterweight 50: Cab
52: operating part 60: working device
70: Boom 72: Boom cylinder
72a: Boom head chamber 72b: Boom rod chamber
76: boom lock valve 80: arm
82: female cylinder 90: bucket
92: bucket cylinder 100: engine
200, 202: Hydraulic pump 210: Hydraulic line
212: return hydraulic line 220: high pressure hydraulic line
222: Boom head hydraulic line 224: Boom rod hydraulic line
230: Hydraulic regeneration line 300: Main control valve
310: Boom control spool 312: Electronic proportional pressure reducing valve
400: regeneration valve unit 410: discharge control valve
420: check valve 430: opening / closing valve
500: accumulator 502: opening / closing valve
510: Hydraulic motor 600: Control unit
610: Bypass valve

Claims (20)

A boom cylinder for operating a boom of a construction machine;
A main control valve having a boom control spool for selectively supplying hydraulic fluid from a hydraulic pump to a boom head chamber and a boom load chamber of the boom cylinder through a boom head hydraulic line and a boom rod hydraulic line;
A regenerating device connected to the boom head chamber of the boom cylinder through a hydraulic regeneration line, for regenerating the energy of the boom cylinder;
A regeneration valve unit installed in the hydraulic regeneration line and having a discharge control valve for controlling a flow rate of hydraulic fluid flowing through the hydraulic regeneration line; And
Wherein the control unit controls the operations of the main control valve and the regeneration valve unit so as to control the operation of the main control valve and the regeneration valve unit, to lower the boom at the first speed by discharging the operating oil through the regeneration unit in the boom- And a control unit for controlling the boom to be lowered to a second speed higher than the first speed by discharging the hydraulic fluid through the apparatus and the main control valve. The hydraulic system according to claim 1, wherein the control unit includes a control valve for applying a pilot signal pressure for opening and closing the discharge control valve. 3. The hydraulic system of claim 2, wherein the control valve is an electronic proportional pressure reducing valve. The hydraulic system according to claim 1, wherein the regeneration valve unit further comprises a check valve installed in the hydraulic regeneration line in front of the emission control valve. The boom cylinder according to claim 1, wherein the regeneration valve unit is provided in a connection line connecting the hydraulic regeneration line and the boom rod chamber, and selectively discharges part of the hydraulic fluid discharged through the hydraulic regeneration line to the boom rod chamber of the boom cylinder Hydraulic system of a construction machine. 2. The construction machine according to claim 1, further comprising a bypass valve provided between an operating portion for operating the boom and the main control valve to block control pressure from the operating portion from being transmitted to the main control valve, system. The hydraulic system of any preceding claim, wherein the control unit controls to open the discharge control valve in the boom down low speed mode and to block control pressure from the operating portion from being transmitted to the boom control spool. The hydraulic system of any preceding claim, wherein the control unit opens the discharge control valve in the boom-down high speed mode and controls the control pressure from the operating portion to be transmitted to the boom control spool. The hydraulic system according to claim 8, wherein operating oil from the boom head chamber is discharged to the drain tank via the boom head hydraulic line and the boom control spool. The hydraulic system according to claim 1, wherein the regenerating device includes a hydraulic motor connected to the hydraulic regeneration line, the hydraulic motor being connected to a drive shaft of the engine to provide a rotational force to the hydraulic pump. 11. The hydraulic system of any preceding claim, wherein the regenerator further comprises an accumulator connected to the hydraulic regeneration line. 12. The hydraulic system of claim 11, further comprising an on-off valve installed on the hydraulic regeneration line connected to the accumulator for selectively supplying hydraulic fluid to the accumulator. Determining whether to use the boom-down high speed mode among the playback modes for recovering the boom energy of the construction machine;
If the boom-down high speed mode is not selected, discharging the operating oil from the boom head chamber through a regenerator connected to the boom head chamber of the boom cylinder by a hydraulic regeneration line to lower the boom at a first speed; And
When the boom-down high-speed mode is selected, the operating fluid is discharged from the boom head chamber through the regenerating apparatus and the operating fluid is discharged from the boom head chamber through the main control valve connected to the boom head chamber of the boom cylinder by the boom- And lowering the boom to a second speed higher than the first speed by discharging the boom. 14. The method of claim 13, wherein determining whether to use the boom-down high speed mode includes selecting either the boom-down low speed mode or the boom-down high speed mode among the regeneration modes. 15. The method according to claim 14, wherein when the boom-down low-speed mode is selected, blocking the control pressure from the operating portion operating the boom from being transmitted to the boom control spool of the main control valve. 14. The method according to claim 13, wherein, when the boom-down high speed mode is selected, transmitting a control pressure from an operating portion that operates the boom to a boom control spool of the main control valve. 14. The method according to claim 13, wherein discharging the operating oil from the boom head chamber through the regenerating apparatus comprises opening a discharge control valve installed in the hydraulic regeneration line. 14. The method according to claim 13, wherein the regenerating device includes an accumulator connected to the hydraulic regeneration line and a hydraulic motor. 19. The method of claim 18, further comprising blocking supply of hydraulic fluid to the accumulator in the boom-down high speed mode. 14. The method of claim 13, further comprising shutting off the hydraulic regeneration line and delivering a control pressure from an operating portion to a boom control spool of the main control valve when the boom down normal mode is selected.

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